The present invention relates to printing paper reversing devices used in image forming apparatus such as copying machines, printers, etc.
Conventionally, there are many image forming apparatus such as copying machines or printers which include a printing paper reversing device for arranging the sequence of sheets of copying paper or performing both-side copy or composite copy.
In these reversing devices, printing paper such as copying paper is discharged to a transfer paper reversing table by switching means provided in the feed passageway of the device. By a back-feed roller provided contactable with the reversing table, the original leading end of the printing paper on the transfer paper reversing table is reversed into the new leading end of the printing paper so that the printing paper is fed toward a conveyance passageway.
In such printing paper reversing device, after a sheet of printing paper is completely fed out by the back-feed roller to the conveyance passageway, the next sheet of printing paper must be discharged to the transfer paper reversing table. Furthermore, the back-feed roller is caused to contact the reversing table in a complex manner. Therefore, the reversing capability is limited and the reversing operation is difficult to speed up.
Another printing paper reversing device is proposed which includes a paper inlet roller and a reversing roller which, instead of a back-feed roller, cooperate to discharge a printing paper guided by switching means to a transfer paper reversing table with one of the rollers, for example, the reversing roller, taking the form of a gear wheel, so that the tailing end of the paper is guided toward a paper outlet roller provided in the vicinity of the inlet of the conveyance passageway by causing the teeth of the gear wheel to engage the tailing end of the printing paper. However, in such device, the guide of the printing paper toward the paper outlet roller may not successfully performed depending on the extent of curl in, or the thickness of, the printing paper. Therefore, in such reversing device, a printing paper having a thickness easy to guide or a printing paper difficult to curl is used. In summary, only a limited or somewhat specified paper can be used.